Magnetic rotator for telescribers



June 1948. w. A. LAUDER El AL 2,442,353

MAGNETIC ROTATOR FOR TELESCRIBERS Filed July 27, 1944 2 Sheets-Sheet lINVENTORS D Waiiace .Alliauder Ed wardFUah oon ATTORN s June 8, 1948. w.A. LAUDER ET AL 2,442,353

MAGNETIC ROTATQR FOR TELESCRIBERS Filed July 27, 1944 2 Sheets-Sheet 2RMINALS JJ RELUCTANCE MOTOR VOLT-ANGLE CHARACTERISTIC 40 WITH SPIRALSPRING LOAD VOLTAGE APPLIED TO MOTOR TE IO 20 3O 4O 5O 6O 7O 8O 90 I00ANGULAR DISPLACEMENT OF ROTOR INVENTORS Wkllace JLLauder Edward 1.621720022 ATTO Patented dune 8, 1948 MAGNETIC BOTATOR FOB TELESCBIBERSWallace A. Lauder and Edward F. Galleon, New

City, N. Y.', asaignors to Telautograph Corporation, New York, N. Y., acorporation of W Application Jul; 21,1944, Serial No. seam 6 Claims. 1This invention relates to a device for .translating a variable A. C.potential into a proportionate mechanical torque, and more particularly,to an A. C. reluctance rotator or motor element for accurately andlinearly translating 9. variable A. C. potential into a high torquemechanical motion without the aidof complicated follow-up mechanismsdependent upon local sources of.

power to produce a high torque response.

This application is a continuation-in-part of our copending application,Serial No. 405,226, dated August 2, 1941, issued as U. B. Patent No.2,355,087 on August-8, 1944, in which one useful application of thepresent invention is described.

In indicating, recording, telemetering, telescribing, control, and othersimilar apparatus, it is frequently necessary to transmitinstantaneously the value of some condition being measured or adjusted.The most common and usually the most convenient method for doing this isto translate the value of the condition into an electric potentialvarying in accordance with the variations in the value of the conditionand to transmit this potential through some available transmissionmedium as by radio, telephone, or electric power lines to some distantpoint where the electrical potential is transformed into a visiblemechanical motion. While it is usually quite easy to translate amechanical motion into an electrical value as by means of apotentiometer, variable inductor, or'variable condenser, it is usualldifllcult to retransform such an electrical value into a mechanicalmotion corresponding exactly to the original condition. This is trueespecially when such mechanical motion must accurately andinstantaneously represent the valuevoi the condition being measured andmust exert sumcient power to operate an indicating, recording and/orcontrolling apparatus without considerable auxiliary equipment.

It is an object of this invention to provide electrical motor means forconverting a variable A. C. potential into a high torque mechanicalmotion.

It is a further object of this invention to provide such a device inwhich the mechanical motion is linearlyresponsive to the A. C.potential.

These and other objects and advantages of this invention, which will bein part obvious and in part pointed out hereinafter, are obtained by themeans described in the following specification, and may be more readilyunderstood by reference to the accompanying drawings, showing one of thevarious possible embodiments of this invention, in which:

Figure 1 is a diagrammatic show p rtly in perspective, of a magnitudetransmitting system including an A. C. reluctance motor embodying theinvention herein described;

Figure 2 is a vertical cross-section of the motor of Figure 1 takenapproximately along the line AA; and

Figure 3 is a graph illustrating the linear response characteristic ofthe motor of Figures 1 and 2 in accordance with the, present invention.

The application of a translating device in accordance with thepresentinvention is best illustrated by its application to a telescribingsystem of the type described in the above-mentioned copendingapplication. In such a system, a translating device in accordance withthis invention is the receiving element of a magnitude transmitting ortelemetering system in which a small and delicatecondition-sensitive-means, i. e., the stylus linkage of the telescribertransmitter, is able to control the position of an indicator of largemass, i. e., the pen linkage of the telescriber receiver, remotelylocated with respect to the condition-sensitive-means. In such acommunications system the translating element in the receiver must actinstantaneously and linearly in order to reproduce an accurate facsimileof the graphic characters traced by the stylus in the transmitter and todo this it must overcome the large inertia of the considerable mass ofthe penmoving mechanism and the friction of this mechanism and of thepen moving over the recording surface. Such a result can be obtained bythe use of a translating device of the type of the present invention.

Referring to Figure 1, a stylus 2 in a telescriber transmitter,generally indicated at 4, moves a linkage mechanism 8, one part of whichcauses a shaft 8 to rotate to move the rotary contact [0 of apotentiometer [2 which is connected across a source of alternatingcurrent potential I! through conductors It and 18. Thus there isproduced between the conductor l8 and the rotary contact it an A. 0.potential, the average value of which is at all times a direct measureof one of the co-ordinates of the graphic character being traced bystylus 2 in telescriber 4. This potential is transmitted throughtransmission lines 20 and 22, respectively, to a point, which may beremote with respect to the transmitting mechanism 4 just described,where the A. 0. potential is supplied to the two terminals 24 and 28 ofa high torque A. C. reluctance motor, generally indicated at 30, made inaccordance with the present invention, to position the rotor 32 thereofin accordance with the instantaneous average value of the A. C.potential impressed on the motor 30. The rotor 32 rotates a shaft 34against the force of a coiled spring'31, to move one side of apendriving mechanism 35 of a telescriber receiver device, generallyindicated at 36. Thus, the shaft 34 continuously maintains a positiondirectly and linearly proportional to one co-ordinate of the graphiccharacter being traced by the transmitter stylus 2.

In a similar manner, the other co-ordinateof the graphic character beingtraced by transmitter stylus 2 is converted into an A. C. potential by apotentiometer device l3, similar to potentiometer l2, from which an A.C. potential corresponding in average value to the other co-ordinate ofthe character being transmitted is carried by transmission lines 20 and2| to another A. C. reluctance motor device 3|, similar to motor 30,which rotates a shaft 33 to move the other side of the pen-drivingmechanism 35 of the telescriber mechanism 36 by an amount directly andlinearly proportional to the other co-ordinate of the graphic characterbeing telescribed. Thus the pen 38 reproduces accurately andinstantaneously the graphic character being traced by transmittingstylus 2.

In accordance with the present invention, the high torque A. C.reluctance motor 30 is provided with a specially shaped rotor 32contoured to produce a linear relationship between the magnitude of theapplied A. C. voltage and the angular position of the rotor 32 whenworking against a load whose torque varies inversely with the angularposition of the rotor, i. e., spring 31. As can best be seen in thecross-sectional view of the motor 30 shown in Figure 2, this motor has arectangularly shaped magnetic field structure 40, preferably made oflaminated silicon steel and held together by clamping frame plates 42clamped together by through bolts 44. One side of the magnetic fieldstructure 40 is provided with an air gap 46 thus forming pole pieces 48on either side thereof. Field coils50, wound around these pole pieces48, are connected in series across the terminals 24 and 26 connected tolines 20 and 22 from the transmitter 4, as above described in connectionwith Figure l. The pole faces 52 of the pole pieces 48 are cylindricallyconcave to receive the rotor 32. The rotor 32 is preferably made of astack of laminatiofis of suitable magnetic material such as siliconsteel, clamped together and secured to the motor shaft 34. Shaft 34 issuitably journaled in bearing plates 54, secured to the bolts 44 passingthrough the clamping plates 42 of the field structure 40, parallel tothe pole pieces 48 as above described. The rotor 32 is givenapredetermined shape, for example that shown in Figure 2, so as toprovide the motor with a straight-line characteristic relationship asabove mentioned. A spiral spring 31 is provided to bias the shaft 34 toa normal position such that the rotor 32 bears the relationship to thepole faces 52 shown in Figure 2 and to provide a torque opposing therotational torque of the rotor 32. One end of the spiral spring 31 issecured toa collar 53 attached to the shaft 34 by'means of a set screw60, the other, end is clamped to a right angle bracket 62 which isadjustably secured tothe front bearing plate 54 by means of a nut 64threaded onto a bearing sleeve 66 secured to the bearing plate 54 as maybe more readily seen in Figure 1. Bracket 62 is suitably angularlypositioned with respect to bearing plate 54 so as to position the rotor32 in its normal angular position with respect to the is attached toshaft 34 by means of a set screw 10 so that the shaft 34, and thereforethe rotor may be suitably positioned longitudinally with respect to thefield structure 40. In order to provide means for adjusting thelength'and therefore the torque of spring 31, a clamping arrangement isprovided on the bracket 62 for clamping the spring 31 to accuratelydetermine its effective length. This clamping arrangement comprises a'bolt 12 passing through the bracket 62 and having a hole 14 in one endthereof through which the end of the spring 31 passes. A nut 18 isthreaded onto. bolt 12 and the other side of the bracket 62 whereby anyportion of the end of the spring 56 can be clamped against the bracket62. In operation, when the field coils 50 are energized, the rotor 32 ofthe reluctance motor 30 thus formed, due to its configuration, tends torotate in the direction shown by the arrow in Figure 2 in an effort toreduce the air gap between the pole faces 52 and the periphery of therotor 32, and thus reduce the reluctance of the magnetic circuit 40.This rotation, however, is opposed by spring 31, and therefore theangular rotation of the rotor 32 is a function of the value of thevoltage across the coils 50 and increases as this voltage increases.

In the embodiment shown, the special form of the rotor 32 causes thisincrease to be linear with respect to voltage. This can be shown by thefollowing analysis. The torque produced in a rotary electro-magnet maybe expressed in the following formula:

where,

T=torque d =rate of change of reluctance, with respect to angle ofrotation.

1 Let g- K3 then The flux is proportional to the alternating potentialapplied, as shown in the formula:

V where V=potential K1=4.44 IN T0- in which,

,f=frequency in cycles per second N=number of turns in the coil.

A linearly varied voltage, to be impressed, may be expressed as:

V= Ka-l-G (4) where,

c=initial voltage K=a constant, being the change in voltage, with thedesired change in angle.

It is desired that the torque vary as a constant function of the angleof rotation. This may be en as:

r=n+1ca (s) where.

Substituting the values in Equations 3, 4 and 5, in

Equation 2:

LELtL da K: (Ka+) and integrating:

r K 0 L 7 08-l -i-l+ a+c +C'1(7) in which, C1 a constant of integration,equals the initial valueof reluctance, when a=0.

In the present embodiment of the invention,

the length of gap is varied as a function of a generating angle, aboutthe center of the rotor 32, which angle equals zero, when the angle ofrotation equals zero. This may be expressed as:

where.

l=air gap length =generating angle.

Now, the infinitesimal permeance of the ga may where, b=included angleunder the pole face 52.

Since the reluctance is inverse to the Permeance, the reluctance isexpressed By equating Formula 11 to Formula 7, the length of gap, foreach angle about the rotor may be determined. This, of course,determines the radius of the rotor for each angle.

Illustrative of the application of the above, in

a particular motor developed the constants were as follows:

Equation 4:

V: Ka-t-C K=1.0 c=34.5 volts.

Equation 5:

T=To+Kgd To=1.6 ounce inches- K:=.144 ounce inches per degree.

6 Equation 11:

a l I b=60 r=.5ii5 inch.

The length of gap required was found to be such that,

- logl= 5.004'2.054 10-' 1.968 X 10-"c10 where, Z=lengthof gap inthousandths of inches.

From this analysis it can be seen that a hightorque A. C. reluctancemotor in accordance with the present invention is provided with polefaces Y surrounding a substantial portion of the-periph-' cry of therotor and having a length of the same order of magnitude as the diameterof the rotor, and in which the entire area of the pole faces areeflectively operative at all positions of rotation of the rotor.

Figure 3 shows the response curve of an actual high torque A. C.reluctance motor constructed in accordance with the invention hereindescribed showing the linear response of such a motor to the A. C.potential impressed thereon.

Although the electro-mechanical translating device of the presentinvention has been described in connection with a telescriber system, itis obvious that its usefulness is not confined to such use, but ratherthat it is applicable to use in any system in which an A. C. potentialis to,

be accurately and linearly translated into a mechanical motion of hightorque, linearly proportional to the value of the actuating A. C.potential. It is to be understood that this invention is capable of manymodifications without departing from its spirit or scope. It is not tobe limited to the precise embodiment shown and described but only asindicated in the claims.

We claim:

1. A high-torque A. C. reluctance motor for providing a controlledrotation of less than comprising, in combination, a C-shaped stator ofmagnetic material having a gap therein or circular cross-section betweenthe ends thereof, a winding encircling said stator for energizing themotor, and a cylindrical rotor of magnetic material rotatably mounted insaid stator gap on an axis coinciding with the longitudinal axis of saidgap, the pole faces of said stator surrounding at least one third of thesurface of said rotor, and said rotor having a cross-sectional radiuswhich continuously and smoothly increases from each of two diametricallyopposite points on its periphery to the other said point to graduallyand continuously decrease the air gap and therefore the reluctance ofthe magnetic path between said rotor and said pole face in a continuousand smooth curve as said rotor rotates to move said given point fromunder said pole face.

2. A high-torque A. C. reluctance rotator for providing a controlledrotation of less than 180, comprising, in combination, a C-shaped statormember of magnetic material having a gap therein of circularcross-section between the ends thereof, a winding encircling said statormember for energizing the motor, a cylindrical rotor member of magneticmaterial rotatably mounted in said stator gap on an axis coinciding withthe longitudinal axis of said gap, said rotor member having across-sectional radius which continuously and smoothly increases fromeach of two diametrically opposite points on its periphery to the othersaid point to gradually and'continuously decrease the air gap andtherefore the reluctance of the magnetic path between said rotor 'memberand said pole face in a continuous smooth curve as said rotor memberrotates to move said given point from under said pole face and whereinthe length of the air gap is determined by the relationship R=desiredreluctance at any predetermined angl of rotation,

l=length of the air gap,

r=radius of the stator gap,

a=angle of rotation,

b=included angle under the pole face,

o=generating angle.

3. A high-torque A. C. reluctance rotator for providing a controlledrotation of less than 180 comprising, in combination, a field structuremade of a stack of laminations of magnetic material forming a magneticcircuit closed except for an air gap having a circular cross-section, afield winding encircling said magnetic circuit for energizing the motor,an armature formed of a stack of laminations of magnetic materialrotatably supported on a shaft in said air gap, said armature having across-section the radius of which continuously and smoothly increasesthrough about 180 from two diametrically opposite points on itsperiphery whereby the gap between said armature and said field structuregradually and continuously decreases as said armature rotates from apredetermined angular position, and a long spiral spring encircling saidshaft and biasing said armature toward said predetermined angularposition to provide a torque opposing rotation of said armature.

4. In a high torque A. C. reluctance motor of the type wherein anelement is moved at a receiving station with true fidelity of responseto the movement of an element at a sending station and wherein thereceiving station is connected to the sending station by circuitchannels carrying alternatin current from the sending station to thereceiving station, the combination of, a C-shaped stator magnetic corehaving a gap between a pair of oppositely disposed pole faces,

said pole faces extending along a circular cylindrical surface andforming a large Portion of the surface thereof, a winding through whichthe current from the sending station flows encircling said .statormember to set up magnetic flux through said stator member thereby toerr-- ergize the motor, a rotor of magnetic material having its axissubstantially coincidental with the axis of said cylindrical surface andhaving a cylindrical peripherial surface which is uniform incross-section in the direction of the axis of the rotor and which variesin radius around the circumference of the rotor,the radius being aminimum at first and second diametrically opposite points on thecircumference and being a maximum at first and second diametricallyopposite points on the circumference with the radius of the rotorincreasing from said first and second points of minimum radiusrespectively to said first and second points of maximum radius and withthe first point of maximum radius being adiacent the second point ofminimum radius and point of'maximum radius being admounting said rotorin said gap with each point of minimum radius of the rotor beingadjacent one edge member tends to biasing tending to hold said rotor insaid predetermined position and tending to oppose said rotation of saidrotor.

5. A high torque A. C. reluctance motor for use in a telescriber systemwherein an A. C. potential, produced at a transmitting station andvaried in accordance with a coordinate of a graphic character to betelescribed, is transmitted to a receiving station through a suitabletransmission medium, where the graphic character is faithfully andinstantaneously reproduced with the reluctance motor moving a pen memberthrough a pen linkage structure, said reluctance motor comprising, incombination, a c-shaped stator member of magnetic material having a gaptherein between a'pair of oppositely disposed pole faces, said gaphaving a circular cross-section and an axial length of the same order ofmagnitude as the diameter of said gap cross-section, a winding adaptedto be connected to an A. C. circuit from a transmitting station andencircling said stator member to set up therein a magnetic flux varyingin accordance with the variations in a coordinate of a graphic characterbeing telescribed, a cylindrical rotor member of magnetic materialrotatably mounted in the gap in said stator member on an axis coincidingwith the longitudinal axis of said stator gap and having a maximumdiameter only slightly less than that of said gap, said rotor memberhaving a noncircular cross-section in which the radius increases"through about from two diametrically opposite points on its periphery,and a long spiral spring encirclin the shaft of said rotor and securedthereto and to a structure attached to said stator member to provide arotational bias in accordance with Hookes law to tend to maintain saidrotor in a position in which the minimum radii of said rotor member areunder one edge of each of said pole faces to tend to oppose rotation ofsaid rotor in a direction which gradually and continuously decreases theair gap between said stator and said rotor as the energization of saidwinding is increased, whereby a linear relationship is produced betweenthe value of the A. C. potential impressed on said winding and theangular position of said rotor member.

6. A high torque A. C. reluctance motor for use in a telescriber systemwherein an A. C. potential, produced at a transmitting station andvaried in accordance with a coordinate of a graphic character to betelescribed, is transmitted to a receiving station through a suitabletransmission medium, where the graphic character is faithfully andinstantaneously reproduced with the reluctance motor moving a pen memberthrough a pen linkage structure, said reluctance motor comprising, incombination, a C-shaped stator member of magnetic material having a gaptherein between a pair of oppositely disposed pole faces, said gaphaving a. circular cross-section and an axial length of the same orderof magnitude as the diameter of said gap cross-section, a windingadapted to be connected to an A. C. circuit from a transmitting stationand encircling said stator member to set up therein a magnetic fluxvarying in accordance with the variations in a oi the respective polefaceof the stator cause rotation of the rotor. and springwherebytheenergization oi the motor means operatively connected to said rotor12,442,858 di te f hi haract bei tel 10 000:: na agrap cc er ngescribed, a cylindrical rotor member of magnetic REFERENCES CITEDmaterial rotatably unted i th gap of id The following references are ofrecord in the stator member on an axis coinciding with the lonfile Of ti p tent: gitudinal axis of said stator gap and having a UNITED TEmaximum diameter only slightly less than that of STA S PATENTS said gap,said rotor member havin a non-circu- Number Name Date lar cross-sectionand comprising two portions 1544371 Tma-nny July 7, 1925 which aresemi-circular in cross-section with Mm'rm et June 1933 their flat sidesin. the same plane and with their 1121-699 Janwl June 21, 1938 axesparallel and oil-set so that the radius of said 2364556 Price 12, 1944ifif ifii *Zu ?1fi$i%i3"$e FOREIGNPATENTS o l e c y op e n s P ery, androtational-bias resilient means connected i gg g' G g Date to said rotormember to bias said rotor member 40665 tam against the torque created onsaid rotor means I Great Britain 1933 by energizatlon of said winding,whereby a linear relationship is produced between the value or the A. 0.potential impressed on said winding and the angular position of saidrotor member.

WALLACE A. LAUDER. EDWARD F. CAHOON.

